The invention relates to a method for transferring biological material arranged, for instance, in a given pattern, wherein the biological material is brought into contact with needles placed on the head of a robot and the biological material is transferred to a support, wherein the needles are hard metal needles fitted with a biocompatible coating. The biocompatible coating preferably consists of metal-nitrogen compounds. Furthermore, preferably, an anticorrosion coating is applied underneath the biocompatible coating. Once the biological material has been arranged in a given pattern, the needles mounted on the robot head are arranged according to the same pattern. Preferably, the pattern corresponds to the pattern of the arrangement of microtitre plate wells. Furthermore, the invention relates to a robot head fitted with the hard metal needles according to the invention. In particular, said robot head particularly forms part of a picking and/or a spotting robot. Finally, the invention relates to the utilization of hard metal needles fitted with a biocompatible coating for transferring, for instance, biological material arranged in a given pattern to a support.
Computer-assisted screening methods are more and more used in biologically or biochemically orientated laboratories. As example, the Human Genome Project has shown there is a need of methods and equipment for the identification and cataloguing of more and more material within shorter and shorter intervals. Robots have been developed in recent years for the screening of gene banks, which have considerably facilitated a systematic screening of the libraries and a subsequent analysis. The robots used in these methods are generally referred to as picking/spotting robots. The currently used picking/spotting robots are capable of picking up biological material and putting it down in a well-aimed way and distributing it. For this purpose, gadgets (needle templates) are used in different designs, for instance, in arrays of 8xc3x9712 or 16xc3x9724. These needle templates are fitted with high-grade steel needles. The high-grade steel needles have a good corrosion-resisting quality but a low mechanical resistance. The use of picking/spotting robots known in the art, therefore, often leads to mechanical deformations and, thus, to bad hitting results (picking) and thus to time-consuming extra work. The use of spotting needles in spotting robots leads to, for instance on high density filters, bad grids of biological material after deformation of the needles.
The problem underlying the present invention was thus to modify the method known from the prior art in a way that putting down and distribution of biological material in a well-aimed manner is guaranteed when using picking/spotting robots. Furthermore, after having been put down and distributed, the biological material should, of course, maintain its biological characteristics to an extent as large as possible.
This technical problem has been solved by providing the embodiments characterized in the claims. Thus, the invention relates to a method for transferring biological material, wherein the biological material is brought into contact with needles placed on a robot head and the biological material is transferred to a support characterized by the needles being hard metal needles fitted with a biocompatible coating.
Surprisingly, according to the invention, it was found that a method according to the above-mentioned general term renders the desired effect if the high-grade steel pins known from the prior art are replaced by hard metal needles fitted with a biocompatible coating. This measure leads to the fact that a high hitting percentage and long-term use of the used robot heads is guaranteed by the met hod of the invention. The such treated hard metal needles have proved to be corrosion-resistant and to generate a minimized friction in the gadget. They are further characterized by a high abrasion resistance and are wear-resistant. The biocompatible coating resulted in a resistance to wear which was 20 times higher than an ordinary gold coating.
By means of the method according to the invention it was possible to achieve a high accuracy concerning the picking and no mechanical deformation was observed. The modifications and deformations of the picking needle known in the prior art which lead to a deterioration of accuracy due to the change of position in the gadget no longer occur. Therefore, the problem of a computer-controlled correction which had been solved insufficiently in the prior art also becomes irrelevant. For the known correcting systems only correct errors concerning the position of the whole picking head. In the case of crooked needles, a correction by means of software was not possible. Therefore, the method according to the invention allows an optimum utilization of the camera-correction system which corrects, above all, errors concerning the position of the picking head. Due to the minimized friction described above there are altogether fewer cases of disturbance due to stuck needles. The cleaning of the picking head is also unproblematic and can, for example, be performed in water. After all, the higher stability/resistance of the needles allow a denser arrangement on the robot head.
In a preferred embodiment of the method according to the invention the biocompatible coating consists essentially or exclusively of TiN, TiCN, TiAlN or CrN. If titanium nitrite is used as a biocompatible coating, the thickness of layer is, for instance, 4 xcexcm at 2400 HV (diamond penetrator hardness (DPH)). The titanium nitrite can, for instance, be applied by means of physical deposition in the vapor phase (PVD, Physical Vapor Deposition). Thus, titanium is vaporized by means of electric arch and, simultaneously, nitrogen is added in high vacuum. The coating temperature is normally below 500xc2x0 C. while there is no structural transformation, no heat casting and no thermal stress. The wear of material is significantly minimized due to the low reactivity of titanium nitrite to ferrous materials. Due to its higher coating hardness the titanium carbon nitrite coating is a good complement to the titanium nitrite coating. It normally exhibits a hardness of 3000 HV (DPH) at a coating density of approximately 3 xcexcm. The titanium aluminium nitrite coating is chosen because of its high hardness and oxidation resistance under the hardest operating conditions. At a thickness of up to approximately 3 mm it has normally a hardness of 3300 HV (DPH). The use of a chromium nitrate coating having a relatively high hardness in combination with a low brittleness allows for the depositing of thicker layers, too. The hardness of this kind of coated needles is approximately 2000 HV (DPH)with a thickness of layer of up to maximally 50 xcexcm.
According to the invention mixtures of the above-mentioned biocompatible coatings are used as well.
In a further preferred embodiment of the method of the invention the hard metal needles are ejector pins or clipping punches. The needles or punches can, for instance, be of alloyed cold work steel (WS), for instance, of material having the material numbers 1.2516, 1.2210 or 1.2842 (e.g. DIN 1530/ISO 6751). When using material no. WS 1.2516 the hardness of the needle head is normally 45 HRCxc2x12 HRC (Hardness Rockwell Cowe), whereas the pin shank of the pinpoint has a hardness of normally 60 HRCxc2x12 HRC. In this preferred embodiment these pins are hardened. The heat-resistance is approximately 250xc2x0 C. After the coating with, for instance, titanium nitrite the ejector pins have a hardness of approximately 2400 HV (DPH). The above-mentioned materials have a retention of hardness of at least 200xc2x0 C. It is ductile hard tool steel with a medium resistance to wear.
Moreover, high-alloyed tool steel (HWS), for instance, material numbers 1.2601 or 1.2379 can be used. These tool steels have a high resistance to wear and a high retention of hardness. If tool steel having the material number WS 1.2379 is used, the pinpoint/the pin shank has a hardness of normally 62xc2x12 HRC. The needle head normally has a hardness of 50xc2x15 HRC. Moreover, high-alloyed high-speed steel (HSS), for example material number 1.3343, can be used in the method according to the invention. Such materials are characterized by highest resistance to wear, good ductility and high heat-resistance. If such steel, for example material number WS 1.3343, is used the pin shank/the pinpoint normally have a hardness of 64xc2x12 HRC, whereas the needle head has a hardness of 50xc2x15 HRC. Moreover, powder metallurgically-produced high-speed (ASP 23) steel is preferably used in the method according to the invention. Such materials have an excellent resistance to wear and an excellent compression resistance and, furthermore, are characterized by high ductility as well as by very good homogeneity of the material. If, for instance, such high-speed steel with material number ASP 23 is used, the pin shank/the pinpoint normally has a hardness of 64xc2x12 HRC. The needle head normally has a hardness of 50xc2x15 HRC.
In a further preferred embodiment of the method of the invention the robot head is the head of a picking robot.
In another embodiment of the method according to the invention the method is characterized by the biological material being arranged in a given pattern and the biological material being brought into contact with needles being mounted on a robot head according to the same pattern. This method is preferably used if the robot is a spotting robot. If this type of robot is used for the replication of the biological material, for putting it into liquid medium, the needles are referred to as replica needles, see FIG. 3.
In a further preferred embodiment of the method of the invention the robot head is therefore the head of a spotting robot. The above remarks as to the advantages of the method of the invention in the embodiment, wherein the robot head is the head of a picking robot, are correspondingly true in the case of the robot head being the head of a spotting robot.
In a further preferred embodiment of the method of the invention the pattern of the arrangement corresponds to the pattern of the wells in the microtitre plate or to the pattern of reactors arranged in a correspondingly regular pattern.
In this embodiment of the method of the invention, for instance, clones having grown in microtitre plates, for instance, from mammalian cells, can be directly transferred to a material which can be used in the screening method.
In a further preferred embodiment of the method of the invention the biological material comprises nucleic acids, (poly)peptides or transformed host organisms. A particular advantage of this embodiment is that the material used for the coating of the hard metal needles is biocompatible. Thus, the biological material can be analyzed further without having to risk losses due to inactivation or chemical degradation. In the case of transformed host organisms, for instance, the latter can be cultured again after transfer into a viable state and thus be analyzed further. Nucleic acids can be analyzed further according to standard screening methods like hybridizations. Polypeptides, for instance, can be further analyzed by means of suitable antibodies, without being subjected to procedural modifications.
In a particularly preferred embodiment of the method according to the invention the transformed host organisms are yeasts, Pistoria- or Saccharomyces-cells, bacteria, preferably E. coli, insect cells, preferably Spodoptera frugiperda cells, fungi cells, preferably Aspergillus cells, plant cells or mammalian cells.
Another preferred embodiment of the invention relates to a method wherein the support is a liquid or a solid support. Particularly preferred in this connection is that the liquid support is a culture medium, a medium for the storage of biological material, a reaction buffer or a staining solution. An example of a reaction buffer is a buffer which is used in a polymerase chain reaction (PCR). In addition to the actual buffer solution which can be produced by the person skilled in the art according to the standard methods the buffer can contain further components of organic or inorganic origin. In another preferred embodiment of the invention the solid support is a nitrocellulose membrane to which nucleic acids or (poly)peptides can be linked, a polyvidendifluoride membrane to which (poly)peptides can be linked, or a glass support, preferably for the application of (poly)peptides or nucleic acids.
Another preferred embodiment of the method of the invention is characterized by the anticorrosion coating being applied underneath the biocompatible coating. Normally the coating placed underneath is applied by means of a first coating whereas the biocompatible coating is subsequently applied onto the needle. A particular effect of the anticorrosion coating is that the needles are protected from rusting. Therefore, they give the needles improved resistance. This is particularly the case if the biocompatible coating is applied by means of evaporation. During evaporization no biocompatible coating is applied onto the suspension points of the needles. At these points additional measures against, for instance, corrosion have been taken when placing an anticorrosion coating onto the needles.
The anticorrosion coating is preferably a nickel coat or a chromium coat. A coating particularly with nickel has also the advantage that the application of this coating can be performed at low cost.
The invention also relates to a robot head, in particular for the performance of the method according to the invention, which exhibits the above-described hard metal needles fitted with a biocompatible coating. It is particularly preferred that the robot head forms part of a picking robot or a spotting robot. Finally, the invention relates to the use of the above described coated hard metal needles for transferring biological material arranged in a given pattern to a support.